In many applications inspection of metal tubular goods for the presence of possible defects is highly desirable and/or required. Inspection of metal tubulars is common in, for instance, the oil and gas exploration and production industry, in refineries and/or in chemical and other plants, where the failure of such tubulars may result in serious consequences.
The art of inspecting metal tubulars for possible defects has experienced various improvements over the course of time. Early testing was rudimentary. It sometimes consisted of no more than visual inspection of the exterior of the tubular for such defects as might be seen. This method was obviously limited. Sometimes inspection might include an attempt to “ring” or “sound” the tubular. This generally involved striking the tubular with a hard object, such as a hammer, and listening to the sound the tubular produced. An abnormally “flat” tone may indicate that the tubular was cracked. This method was highly subjective and even if employed by skilled personnel was unable to detect small defects.
The need to improve inspection of metal tubulars led to other developments, such as magnetic testing. One method of magnetic testing involved magnetizing the tubular (or a portion thereof), “dusting” same with ferromagnetic powder and then visually inspecting for abnormal distribution of the powder. In another method of magnetic testing an electromagnetic coil was passed close to the surface of the tubular and various means used to determine disturbance of the induced eddy current possibly being caused by discontinuities in the tubular. Neither method was well suited for detection of small defects and/or those below the surface of the tubular, were time consuming, were largely dependent on the skill of the operator and did not produce precise data from which the effect of a condition found might be mathematically calculated.
Another attempt to improve inspection of metal tubulars was the dye penetrant method. In such method the tubular was cleaned, coated with a penetrating fluid containing dye (typically of a type which would fluoresce under certain lighting conditions), wiped and then visually Inspected for surface discontinuities still containing dye. This method was not useful for detection of sub-surface defects and did not produce precise data from which the effect of a condition found might be mathematically calculated.
Another means to inspect metal tubulars is by utilization of X-rays. While x-ray represents a way to determine some defects below the surface of the tubular wall, certain defects such as thin cracks and delaminations are difficult to find by X-ray. Moreover this method of inspection does not produce precise data from which the effect of a condition found might be mathematically calculated. Because of the danger, shielding requirements, expense and limitations of this technology, its use has been limited.
An attempt to Inspect metal tubular goods for wall thickness defects was represented by utilization of gamma radiation. In one method the gamma source is placed on one side of the tubular and a radiation sensor on the other side of the tubular. By measuring the decrease in radiation as it passes through the tubular an estimation of the collective wall thickness of both sides of the tubular can be made. This method has certain disadvantages, including but not necessarily limited to relative insensitivity of the sensor to small thickness changes, its inability to detect if one side of the tubular is thick and the other thin (which is not an uncommon defect, particularly in extruded tubulars) and the safety, security and administrative issues relating to utilization of radioactive sources. Moreover such inspection does not produce data from which the effect of a condition found might be calculated with mathematical precision.
In attempt to avoid the limitations of the above technology, ultrasonic technology was developed for inspection of tubular goods. In general, this technology is based on the speed of sound in metal and the fact that a sound wave will reflect (“echo”) from medium interfaces. Thus by propagating a sonic wave in said metal and by measuring the time it takes for echos of that wave to return from an interface, it is possible to determine the precise distance to said interface. Such interface may, of course, be the opposite wall of the tubular. Accordingly by use of ultrasonic means precise wall thickness of a tubular at an area may be determined. In order to determine the wall thickness of a tubular about the whole area of the tubular, the tubular is typically rotated about its axis and advanced longitudinally in relation to an ultrasonic head which periodically “fires” and effectively samples wall thickness under the head at the time. As the tubular advances a stream of data points, each one representing a wall thickness measurement is generated. Typically the data resulting from such testing is displayed in two-dimensional form, as a numeric table or as a line on a graph (representing wall thickness at a position on the length of the tubular). Out-of-range values can be detected either by human reading the table or graph, or by machine (computer) detection of out of range values. From such data the general location of a suspected defect along the length of tubular, its magnitude and direction (whether too thin or too thick) can be determined and the tubular joint marked for acceptance, rejection or repair, but said data was not useful for substantial purposes therebeyond. Namely, without three-dimensional data as to both the defect and the remainder of the tubular, the effect that defect might have concerning performance of the tubular could not be calculated with mathematical precision.
The invention disclosed herein relates to improved method to acquire, collect, assemble, store, display and/or utilize data stemming from ultrasonic inspection of tubular goods, not only for a determination for the presence or absence of defects, but so that data from the inspection may be used to calculate projected performance of the tubular with a mathematical precision not previously available by non-destructive evaluation of the tubular.